Lithium-based rechargeable battery is conventionally charged by using Constant- Current, Constant-Voltage (CC-CV) method. The charging voltage rises rapidly to the battery cell upper voltage limit typically 4.2 Vpc (Voltage per Cell), and then maintained at that level. The cell current maintains constant with the rise of charging voltage and starts to decrease when the charging voltage hits the upper level limit. The charging current is cut off when it reaches a predetermined minimum current point which indicates a full charge.
All batteries have a limited lifespan. Charging rate of rechargeable battery has a great impact on length of lifespan of the battery. Fast charging causes increased Joule heating of the cell because of the higher currents involved and the higher temperature in turn causes an increase in the rate of the chemical conversion processes. Frequently fast charging will overstress the battery cells causing them to become weak until they eventually fail and shorten the battery life. The way of charging directly affects the charging rate and further the battery lifetime. In conventional charging process, charging behavior is normally independent of other external parameters than battery type and temperature. Nowadays battery has been widely used in all kinds of battery powered end user devices, for example, portable mobile phone, phone with car kit, camera, laptop etc. Short battery life will cause bad user experience. It is expensive to frequently replace a rechargeable battery.